Controlling Exposure on the HV20: Walkthroughs and Tutorials.

[Jason Ramsey]

Several folks have put togethor their own little walkthroughs and tutorials, etc. on how to do this, so I figured we'll just go ahead and get them all in one place for easy reference.

Barry's article/write-up:
http://www.dvxuser.com/V6/showthread.php?t=96502

And, thanks to jenningsp for this little video tutorial:
http://hv20.info/yopu/hv20aperturecontrol.mov


Thanks folks.
Jason

If there are any other helpful ones, post them below and I will add them above.

[Dennis Wood]

Jason, that link I posted is the same one as linked to from the HV20.com site by jenningsp :-)

[Jason Ramsey]

oops. :) Thanks.

Jason

[jenningsp]

learning is fun :)

[dmoreno]

Thanks a lot for the great tutorials and valuable information. I just wanted to give you a hint that has been useful for me. Instead of using the "cellular trick" to get the desired initial exposure I use the built-in led light reflected on the palm of my hand. Just try different distances until you get the exposure you want (ie: 1.8, 1/48 shutter)

[Ian-T]

Does this only work for Cinemode or can one use this technique in TV mode also?

[marko5000]

What confuses me is why would you want to.

No gain is important but all these techniques get rid of gain by underexposing the image don't they?

These methods would be good to controling the settings if you are also in control of lighting.

Am I right in thinking that in difficult lighting you decide between a grainy image and an underexposed one?

I understand that if you can't control the lighting you have to compromise but I was wondering if people are getting real world benefits from these changes or if this is really just a technical exercise without real application.

Sorry for the long post. And I am not being negative. I think the advice people offer on here is invaluable I am just struggling to understand the best was to approach this (I have no lights).

Is this advice just not for me?

[SenorKaffee]

My opinion is, if there is a need to digitally enhance the picture I could still do that in my NLE.
Maybe I only need to add "digital light" to a few spots and the rest is fine.

Since my stupid Nokia 6230i doesn´t want to stay lit long enough I´m thinking about other way. Maybe a sheet of white paper with a flashlight behind it. All tricks are hard to do with a single pair of hands.

If it is possible to take a laptop with Firewire with you, you can also use the HDV Data Monitor. The tool is written for Sony HDV cams and sometimes doesn´t interpret the Shutter speed right on Canons, but it shows you the gain settings.

[Cranky]

I found out about Barry's article after I wrote my own. His article seems to garner quite a reputation in HV20 world. He admits that there is an "easy way" with a memory card, but still tries to figure out predictable aperture measurements/settings using "hard way". Why? Beats me. 2GB memory card costs mere $20, not worth going the "hard way".

I have a different take on the whole "manual exposure control" issue. The difference is that I own the Elura 100, not the fancy HV20, but don't you worry, the principles are all the same throughout Canon camcorders and my friend got the HV20 so I played with it.

Basically, just read the articles at the links below, it is simpler than retyping them here on this forum:

http://www.elurauser.com/articles/light_meter.jsp
http://www.elurauser.com/articles/manual_mode.jsp

You will learn:
* How to read light meter measurements.
* How to find out whether gain is elevated or not. I don't care about particular gain levels. (Oh, by the way, this small application reports gain, shutter speed, aperture and other stuff for your DV AVI footage: http://www.dvmp.co.uk/dv-media-player.htm I don't think it understands HDV though.)
* How to change aperture manually while keeping shutter speed locked, and to be able to verify current settings.
* How to calculate how many ND filters you need to open up iris while preserving current exposure (here "exposure" is indeed overall exposure, not aperture).

You might find my EXP/aperture table handy for calculations:

http://www.elurauser.com/articles/manual_mode_aperture_table_hv20.gif

---
Michael, Canon Elura User Pages (http://www.elurauser.com)

[rur]

Is it okay to just leave the auto exposure on? I found that the lighting does change a bit as it adjusts with the auto exposure on. Is this okay, or should you always set the exposure manually?

[tcindie]

I know this is an older thread.. but I didn't see a better place to post.

I know the cellphone trick is pretty widely used, and I'm sure all phones yield slightly different results. Just thought I would share the results I get with my Samsung t-809.

I use an all white image as my background image, so all I have to do is slide the phone open to activate the backlight. I have the backlight brightness level set to maximum (5), and this allows me access to the FULL range -11 to +11 on the HV20 exposure scale.. I get from f7.8 to f2.6 with every point on the scale locked at 1/48th. :D

[Zephyrnoid]

Sorry to seem like the dimwit at times. I tried to condense this amazing "psuedo manual without the Gain" tutorial for myself and this is what I ended up with. If someone could please eliminate the 'fat' and just give us the definitive cheat sheet on this issue, I'd be much obliged to say THANKS!

Plan A (Default HV20 Exp Override Functionality)
ACTION: EXP lock function: Press the joystick in>toggle down to EXP> toggle the joystick “up”.
RESULT> A numerical scale, which can range as far as –11 to +11 (varies depending on the prevailing lighting conditions EXAMPLE: 0 to +10, or from –10 to 0
OBJECTIVE: Locate & Set parameter combinations that result in 1/48 shutter, no electronic gain, and a range of iris settings and we’ll be able to repeat those settings in the field.
-------------
Plan B (Max Aperture & Gain @ f/1.8)
ACTION: EXP lock function
1) Zoom to Full Wide With Lens Cap On
2) Shutter Priority Mode (Tv)
3) Shutter Speed = 1/48
RESULT> F/1.8 aperture = 27dB Gain
-------------
Plan C
ACTION: EXP lock function
1) Zoom to Full Wide With Lens Cap On
2) Cine Mode
3) HDV 24P
RESULT> @ F/1.8 aperture

EXP Shutter Iris Gain
+3 1/8 f/1.8 10.5dB
+2 1/15 f/1.8 10.5dB
+1 1/15 f/1.8 9dB
0 1/24 f/1.8 9dB= Default Based On Dead Black 'Subject'
-1 1/24 f/1.8 7.5dB
-2 1/24 f/1.8 6dB
-3 1/24 f/1.8 4.5dB
-4 1/24 f/1.8 3dB
-5 1/24 f/1.8 1.5dB
-6 1/24 f/1.8 0dB
-7 1/24 f/1.8 0dB
-8 1/30 f/1.8 0dB
-9 1/30 f/1.8 0dB
-10 1/30 f/1.8 0dB
-11 1/48 f/1.8 0dB = Film Look Setting
-------------
Plan D (Fixed Shutter & Gain Variable Aperture)
ACTION: EXP lock function
1) Zoom to Full Wide- With Fixed Illumination Cap
2) Cine Mode
3) HDV 24P
RESULT> Fixed Shutter Speed & Varied aperture range

EXP Shutter Iris Gain
+6 1/48 1.8 0dB
+5 1/48 2.0 0dB
+4 1/48 2.2 0dB
+3 1/48 2.4 0dB
+2 1/48 2.6 0dB
+1 1/48 2.8 0dB
0 1/48 2.8 0dB = Default Based On Target Illuminator
-1 1/48 3.4 0dB
-2 1/48 3.4 0dB
-3 1/48 4.0 0dB
-4 1/48 4.0 0dB
-5 1/48 4.8 0dB
-6 1/48 4.8 0dB
-7 1/48 5.6 0dB
-8 1/48 5.6 0dB
-9 1/48 5.6 0dB
-10 1/48 5.6 0dB
-11 1/48 5.6 0dB

*An ideal accessory item would be a lighted lens cap, something that would cap the lens and deliver a repeatable (and appropriate) amount of light. I can simulate that with the “cell phone trick,” but it’d be more professional and repeatable if we could find a fixed light source to use (and, if it was a tad brighter, we could use the full EXP range instead of my current system that allows only up to +6).

[MOJE]

Hey Boys,

With "Enosoft DV Processor" software You may wiev on PC (throught IEEE1394) actual gain (only DV mode on HV 20)

:-)

CINE MODE max GAIN is +9

[Zephyrnoid]

Dead silence??? Anyone wanna make this into a simple cheat sheet?

[Ian-T]

I don't know why one really needs the cellphone ...all I do is use a white piece of paper...turn on the video light...shine it on the white piece of paper ...and lock my exposure...so far the best I have done is get to +9 @ F/1.8 -- 1/48 shutter...every time.

I don't know...but I think it's pointless to try and get the whole range of the exposure...I mean...then what? As long as you can read f/1.8...you are gravy...just add light to your scene if you need to...but at least you have a ceiling of acceptable video to work with...just don't go any higher with your exposure and add light if it's too dim ....right?

[tcindie]

You don't ALWAYS want to run wide open, so having use of the full range gives more control.

[TimeKoder13]

So I bought a miniSD today at CC 1GB $15 on sale from $34...now what??? hehe, I gotta tredge thru that youtube thing, the guys voice put me to sleep 3X already...but hey, thx for the effort...

[Zephyrnoid]

Does this actually work as advertised or is it just a theory?

[DavidD]

DVX users,

I just finished the long road of testing and development of a lighted lens cap called the "Lytecap" - for the Canon HV20/HV30 that gives the user the ability to set the aperture at 2.8 (or any range) whenever they desire. At 2.8, there is 0dB of gain to the image from the range of +6 to -11 when clicking through the exposure.

The Lytecap fits over the barrel of the hv20/hv30 and makes setting the aperture easy as pie.

Have a look at the site :

http://www.lytecap.com

I am a member here, so I hope this is taken the right way - just trying to get the word out to help the hv20 owners and budding film-makers (it will help me as well, I can't lie).

[Mr B]

David, that light cap looks great, have you had a chance to get and use it yet? I went out the other night and used my phone, I got decent results but would like something easier, better, and less fragile :P

[DavidD]

I had a video podcast shoot on Thursday with two HV20's. It was essential that I set both to 2.8 aperture (for that sweet filmic-look) so they both would have the same aperture and exposure - I did it with the Lytecap. It was easy and quick. It was a nice 'real-world' test considering most of my testing done before I went public was in my basement. So to answer your question - yes it works and works well, IMHO.

[DavidD]

Ok, I finally put up a video showing a walk-through of using the Lytecap (where I found time to do this, is still a mystery to me).

http://www.lytecap.com/multimedia.htm

[TimeKoder13]

Do you normally use the sd card? I couldn't figure out why you needed the Sony to read the settings. Had me rethinking my understanding of locking the aperture and using the exp dial for a sec. Then I realized as my Fstops were changing that I was doing the same thing you were doing only I was taking my readings from the HV half pressed shutter button rather than the Sony as I stepped up and down. I know how useful the Sony's are tho, I used to get data for my friend's GL footage all the time in my VX2K.
Now your cap and 2.8. Please bare with me as I'm confused again b/c I thought with regards to mini35, the lenses of choice in the 50mm range were F1.4 and 1.8. Is 2.8 a clear sweet spot for the Canon stock lens or is that just your preference? Thx for your time.

OK, now I see. I know the corresponding gain values on the HV so much that I forget we don't actually see the gain numbers in dBs like with the Sony data code.

[DavidD]

Yeah, the sony HC1 is great for that.
As for preferences, I am finding that 2.8 yields a great picture and I use it all the time. I recently did a test on my blog that shows the difference between an aperture of 2.8 and 4.8 - both maxed out without Gain - to my eye, the 2.8 is sharper and a tad bit brighter. I am still checking other aperture settings as I go, trying to find the perfect one. With 4.8, you get a great range on the EV (all the way to +11). This is nice because each notch brightens the image a little more.

[AndrewGentle]

My opinion is, if there is a need to digitally enhance the picture I could still do that in my NLE.
Maybe I only need to add "digital light" to a few spots and the rest is fine.

Correct me if I'm wrong but wouldn't it be better to apply gain to the image before it was compressed? I assumed that since the camera has access to the image before it becomes 4:2:0 MPEG that any gain which was applied would be more accurate than a brightness increase in post.

[DavidD]

It is better to have NO gain from the camera because it usually results in artifacts and added grain to the image.

[AndrewGentle]

It is better to have NO gain from the camera because it usually results in artifacts and added grain to the image.

I agree, not using gain at all is ideal. I'm asking, if you were forced to digitally brighten the image, would amplification of the sensor information be cleaner if it were applied before compression?

[DavidD]

I would assume any kind of processing if going to be better before compression...but that is not my field - someone else might be better suited to answer that one.

[Zephyrnoid]

I venture that any algorithm such as gain, applied before compression is 'cleaner' if by cleaner you mean less artifact laden . That's because video compression is always lossy itself and that lossiness accentuates artifacts which will appear once gain (a filter) is applied. Same principle is true for still image processing. Gain is death IMHO. Useful only in surveillance images.:violent5:


I agree, not using gain at all is ideal. I'm asking, if you were forced to digitally brighten the image, would amplification of the sensor information be cleaner if it were applied before compression?

[arthur071169]

I an anewbie, so apologies.
I am looking into buying a HD camcorder and after a lot of research (www.camcorderinfo.com (http://www.camcorderinfo.com)) the hv20 isa clear winnder in my eyes.

The Litecap seems to be an idiotproof way of locking the exposure, and the video tutorial shows as much. I am curious however why the value of 2.8 was used for the demo, against the recommended by others 1.8?

The video on Vimeo of the auto versus locked at 1.8 nightime driving also sold me on the fact that this is a great handheld. I am considering getting the lytecap also, but would like a bit more 'road tested' advice as I intend getting one specifically for a holiday I have coming up in a couple of weeks.

Once you lock the exposure, is this setting retained after a power down? (I would be buying an sd card also).
If not retained, do you have to do the procedure based on the 'initial' environment or will adding the cap (in a dark room , or outdoors in bright sunshine) and following the instructions always yield the same end result prior to filming even if moving from outdoors to indoors following a single shot?

thanks for all your patience guys, this is quite new to me, and you have to start somewhere (hence the research on the website listed above).

Arthur.



Yeah, the sony HC1 is great for that.
As for preferences, I am finding that 2.8 yields a great picture and I use it all the time. I recently did a test on my blog that shows the difference between an aperture of 2.8 and 4.8 - both maxed out without Gain - to my eye, the 2.8 is sharper and a tad bit brighter. I am still checking other aperture settings as I go, trying to find the perfect one. With 4.8, you get a great range on the EV (all the way to +11). This is nice because each notch brightens the image a little more.

[Sandra Koponen]

Please let me know where it is explained how to control the exposure on the HV20 using the mini SD card---prefer to do it the easy way!! Not clear from the posted article what steps one takes for the mini SD card method. Thanks!

[Barry_Green]

When you have the mini-SD card installed, then when you push down the "photo" button halfway, the display will show what f-stop you're at. So you control exposure normally, with the EXP slider, but you can at least spot-check and see what f-stop the system is selecting.

[k3vinTran_Dir]

check out this guys work with the hv20 maybe he can answer a couple of questions people seem to have trouble with

www.youtube.com/k3films

he shoots all in hv20 with 35mm adapter

[healthinsider]

Ok, I finally put up a video showing a walk-through of using the Lytecap (where I found time to do this, is still a mystery to me).

http://www.lytecap.com/multimedia.htm
:thumbup: (http://mihealthinsider.com/) Thanks for the guide.